Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook, Page: 138 / 204

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Indoor
Outdoor
Indoor
Outdoor
Indoor
Outdoor
Indoor
Indoor
Outdoor
Failure Mode Judgment Method Treatment Affected LEV
Microcomputer
Driver Circuit
Failure
LEV mechanism
is locked.
The LEV motor
coils have a
disconnected wire
or is shorted.
Fully Closed
Failure (valve
leaks)
Faulty wire
connections in the
connector or faulty
contact.
Disconnect the control board connector and connect the
check LED as shown in the figure below.
When the base power supply is turned on, the indoor LEV
outputs pulse signals for 10 seconds.
If the LED does not light up, or lights up and remains on,
the driver circuit is abnormal.
If the LEV is locked up, the drive motor turns with no load
and a small clicking sound is generated.
Generation of this sound when the LEV is fully closed or
fully open is abnormal.
Measure the resistance between the coils (red - white, red
- orange, brown - yellow, brown - blue) using a tester. They
are normal if the resistance is within 150
Ω ±
10 %.
Measure the resistance between the coils (gray - orange,
gray - red, gray - yellow, gray - black) using a tester. They
are normal if the resistance is within 46
Ω ±
3 %.
If you are checking the indoor unit’s LEV, operate the
indoor unit in fan mode and at the same time operate other
indoor units in the cooling mode, then check the piping
temperatures (liquid pipe temperatures) of the indoor unit
by the operation monitor through the outdoor unit controller
board. When the fan is running, the linear expansion valve
is fully closed, so if there is leakage, the temperature
sensed by the thermistor (liquid pipe temperature sensor)
will become low. If the temperature
is considerably low compared to
the remote control’s intake
temperature display, it can be
judged that there is a fully closed
failure. In the case of minimal
leakage, it is not necessary to
replace the LEV if there are no
other effects.
1 Check for pins not fully inserted on the connector and
check the colors of the lead wires visually.
2 Disconnect the control board’s connector and conduct
a continuity check using a tester.
In the case of driver circuit
failure, replace the indoor unit’s
control board.
Replace the LEV.
Replace the LEV coils.
Replace the LEV coils.
If there is a large amount of
leakage, replace the LEV.
Check the continuity at the
places where trouble is found.
Linear
Expansion
Valve
Thermistor
Judgment Methods and Likely Failure Mode
Caution
The specifications of the outdoor unit (outdoor LEV) and outdoor units (indoor LEV) differ. For this reason, there are cases
where the treatment contents differ, so follow the treatment specified for the appropriate LEV as indicated in the right
column.
<LEV2>
LED
1k
Ω
<LEV1, SLEV>